Bidirectional optical modules are known which communicate with one another using a monomode glass fiber in the opposite direction. The modules comprise a transmitting component, a receiving component and an optical arrangement, by means of which the beam paths are superimposed and split. The light that is emitted from the transmitting component generally, but not necessarily, is at a different wavelength than the light which is detected by the receiving component. For example, the transmitting component emits light at a wavelength of 1300 nm, and the receiving component detects light at the wavelength of 1550 nm. A module of the cited type is known from WO 99/54594 A1. A partially reflective mirror which acts on a wavelength-selective basis is provided in order to split the beam paths, is arranged at an angle of 45° in the beam path of the fiber, and outputs light at a wavelength at an angle of less than 90°. If operated at the same wavelength, instead of a mirror that acts on a wavelength-selective basis, a partially reflective mirror is used. The known bidirectional module disadvantageously requires relatively complex optical and mechanical design technology.
The use of polymer fibers with a diameter of 1 mm for bidirectional communication at the same wavelength is known from the automotive field. Bidirectional modules with a relatively large receiving diode are used in this case. An LED chip is fitted to the center of the receiving diode. The photodiode is admittedly partially shadowed by the LED chip, but the sensitivity of the transmission quality is sufficient for automotive applications. A corresponding design is described in DE 100 64 599 A1.